Aid agencies are in a "race against time" to save thousands of Rohingya refugees from the dangers of the impending monsoon season.

The United Nations High Commissioner for Refugees (UNHCR) has identified 150,000 people at "high risk from mudslides and floods" due to the heavy rain, which is set to hit the eastern part of Bangladesh over the next few months.

The region is also vulnerable to tropical cyclones, as the funnel-shaped northern section of the Bay of Bengal amplifies storm surges, making them devastating almost every year.

Refugees are still crossing over from Myanmar, though not in quite as large numbers as witnessed last year, with 7,400 people having journeyed into Bangladesh so far in 2018.

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Video:Full special report: Rohingya refugee crisis

Firas Al-khateeb, UNHCR communications officer, told Sky News: "Though we cannot relocate the whole population, we are trying to minimise the risks by fortifying homes, using sandbags for pathways and making waterways to channel the excess water."

In 1991, Cyclone Gorky killed 139,000 people in the cities of Cox's Bazar and Chittagong, and rendered another 10 million people homeless.

While data shows the intensity of cyclones has been less severe in recent years, makeshift bamboo and tarpaulin homes still stand no chance against winds that could reach 90mph.

Shelly Thakral, of the World Food Programme (WFP), told Sky News it is a "race against time" to ensure the Rohingya are not left exposed to the potentially deadly conditions.

Image:A new camp is being built to relocate Myanmar refugees in Bangladesh

She said: "We have to do everything possible. WFP is racing to finish a 123 acre plot so that we can relocate 12,000 of the most vulnerable before the rains hit, but then this is a small proposition."

The Kutupalong refugee camp near Cox's Bazar houses more than 700,000 Rohingya, making it the largest refugee settlement in the world.

Humanitarian agencies are reliant on the Bangladeshi government to allocate land for any relocation, but the land provided is forested and hilly, requiring a lot of work in cutting, levelling and stabilising the ground before people can be moved there.

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Video:Rohingya refugees warned of flood risk

In addition, the repatriation process agreed by Bangladesh and Myanmar, which was to begin in January, has been a non-starter up until now.

Bangladesh has provided 8,000 names for repatriation, but Myanmar has refused to take them back.

At a gathering in London on Tuesday, Bangladesh Prime Minister Sheikh Hasina said: "The international community needs to put more pressure on Myanmar so that they take back their own people and ensure their security."

On Saturday, Myanmar officials said they repatriated a family of five who had returned to western Rakhine. The Muslim family was photographed with Myanmar officials receiving their national verification cards.

But Bangladeshi home minister Asaduzzaman Khan said it was "nothing but a farce", claiming that the family never even reached Bangladesh "as they used to live on no-man's land and had never crossed into our territory".

Image:The island chosen for development regularly floods

The Bangladeshi government is also developing the remote Bhasan Char island, which is about 21 miles off the mainland, to shift 100,000 refugees.

It grew out of the sediments just two decades ago and is being developed as an alternative, but the island often gets flooded for many months of the year.

Mr Al-khateeb told Sky News the UNHCR had not been consulted on the project.